This invention relates to an information reproducing system which reads dot codes from an information recording medium on which dot codes composed of data dots, pattern dots to determine a reading point for each data dot, and markers have been recorded in a specific format in such a manner that they can be read optically. More particularly, this invention relates to an information reproducing system capable of preventing block data from being partially lost due to the disappearance of markers or the occurrence of erroneous markers and reducing the marker sensing process.
The assignee of the present invention has disclosed an information recording medium and information reproducing system in EP 0,717,398 A2 (corresponding to U.S. Ser. No. 08/571,776). The information reproducing system has optically read dot codes from an information recording medium on which dot codes composed of data dots, pattern dots to determine the reading point for each data dot, and markers have been recorded. The system has then reproduced the information corresponding to the data dots, the information including audio data, video data, and text data.
In the information reproducing system, a block is composed of data dots, pattern dots, and markers larger than those. One marker is first sensed from the imaging screen and another marker adjacent to the marker is sensed using the first sensed marker as a reference. Using pattern dots between the two sensed markers, reading points for data items in a block are determined. Each data dot is read at the each reading point to reproduce information. Because the reading points for data items in a block are determined using markers and pattern dots constituting a block and the data is read and reproduced, the system is excellent in the reliability of reading densely recorded data and has the great advantage that it is immune to distortion and that it can read even when the imaging device has lifted from or tilted to the recording medium because of manual scanning.
Although the effect of determining the reading points for data items in a block using markers and pattern dots constituting a block and reading data items is great, particular attention should be given to the disappearance of markers and the occurrence of erroneous markers.
To overcome the problems, a system for sensing a first target marker near the center of the imaging screen, a system for limiting an adjacent marker sensing area on the basis of a format, and a system for removing erroneous markers on the basis of marker pairs have been disclosed in EP 0,717,398 A2. Those systems prevent the block data from being partially lost due to the disappearance of markers or the occurrence of erroneous markers and avoid code reproduction failure.
Measures to deal with the disappearance of markers or the occurrence of erroneous markers leave ample room for improvement.
For instance, a recording medium having coated surface is likely to perform regular reflection, moving a luminous point to the marker. Consequently, the marker cannot be detected, making it impossible to read the data in a block that includes the marker. As a result, the block data is inevitably lost. This may cause a code reproduction failure. Furthermore, shading in the periphery of the imaging screen deforms dots. As a result, a pattern similar to a marker is imaged in the data dot recording area in the periphery of the imaging screen. Such pattern is an erroneous marker and may also cause a code reproduction failure. Moreover, because any marker used is larger in area than a dot, it is susceptibly to the influence of poor recording or a flaw in the surface of the recording medium. Therefor, the marker may not be detected even if data dots have been correctly recorded.
The object of the present invention is to provide an information reproducing system capable of not only preventing the block data from being partially lost due to the disappearance of markers or the occurrence of erroneous markers but also reducing the marker sensing process.
According to an aspect of the present invention, there is provided an information reproducing system which optically reads a dot code from an information recording medium and reproduces information, the information recording medium on which an optically readable dot code has been recorded, the dot code composed of blocks arranged in array, each block including at least a data code made up of data dots arranged according to the contents of data related to information to be reproduced, a pattern code placed so as to have a specific positional relationship with the data dots and made up of pattern dots to determine reading points for the data dots, and markers to sense the pattern dots placed so as to have a specific positional relationship with the pattern dots and recorded in a manner different from the data dots and the pattern dots, the information reproducing system comprising:
image input means for shooting the dot code on the information recording medium;
representative marker sensing means for sensing one of the markers on the image shot by the image input means;
pattern dot sensing means for sensing the pattern dots on the basis of the position of the representative marker sensed by the representative marker sensing means;
data dot reading point determining means for determining a reading point for each data dot on the basis of the positions of the pattern dots sensed by the pattern dot sensing means;
data reading means for reading each data dot at the reading point determined by the data dot reading point determining means; and
data reproducing means for concatenating the data items in each block read by the data reading means and reproducing the information.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.